Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932177AbWEPRjK (ORCPT ); Tue, 16 May 2006 13:39:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932176AbWEPRjK (ORCPT ); Tue, 16 May 2006 13:39:10 -0400 Received: from py-out-1112.google.com ([64.233.166.177]:15206 "EHLO py-out-1112.google.com") by vger.kernel.org with ESMTP id S932177AbWEPRjI (ORCPT ); Tue, 16 May 2006 13:39:08 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:user-agent:mime-version:to:cc:subject:references:in-reply-to:content-type:content-transfer-encoding; b=daUaJji/ZR275JIGK4CKxq9tViIboz4rAilSPeO9Jh/A59pLNdDY3R5riAAH+G8wztbsKeRvfM/L0oFn06jI+n6uONGPrV/8Lfn0Cfv8+bGTzTw9a+WZOxXczt4hYSisGoyWw43NkvtVbm2/QHVJ87SF+GhS+uSaKIDGoVEt1pM= Message-ID: <446A0E36.5060505@gmail.com> Date: Wed, 17 May 2006 02:39:02 +0900 From: Tejun Heo User-Agent: Thunderbird 1.5.0.2 (X11/20060501) MIME-Version: 1.0 To: Jeff Garzik CC: Kevin Radloff , Alan Cox , linux-kernel@vger.kernel.org Subject: Re: PATCH: Fix broken PIO with libata References: <1147790393.2151.62.camel@localhost.localdomain> <3b0ffc1f0605160833k5f6355c5n3f2a9ab1b211a95@mail.gmail.com> <1147794791.2151.71.camel@localhost.localdomain> <3b0ffc1f0605161019j7149f72bv309db19eb9d12dd8@mail.gmail.com> <446A0B6C.8050901@garzik.org> In-Reply-To: <446A0B6C.8050901@garzik.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1341 Lines: 32 Jeff Garzik wrote: > Kevin Radloff wrote: >> On 5/16/06, Alan Cox wrote: >>> On Maw, 2006-05-16 at 11:33 -0400, Kevin Radloff wrote: >>> > However, I still have a problem with pata_pcmcia (that I actually >>> > experienced also with the ide-cs driver) where sustained reading or >>> > writing to the CF card spikes the CPU with nearly 100% system time. >>> >>> That is normal. The PCMCIA devices don't support DMA. As a result of >>> this the processor has to fetch each byte itself over the ISA speed >>> PCMCIA bus link. >> >> Hrm, as I recall that only started happening with ide-cs sometime in >> the single digits of 2.6.x.. And note that it's only maxing out at >> about 1.5MB/s. Should that saturate my laptop's 1.1GHz Pentium M >> processor? > > Doing data xfer using PIO rather than DMA definitely eats tons of CPU > cycles. Yeap, in addition, if doing real PIO (unbuffered by the HBA), the time it takes is soley determined by what PIO mode is in use. It doesn't matter how fast the CPU is. Faster CPUs only end up wasting more cycles. :-( -- tejun - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/